Infectious disease caused by bacterial and viral pathogens pose important challenges in prevention, protection and therapy. Microbial carbohydrates co-evolved with the carbohydrates of their mammalian hosts and provide camouflage to pathogens, a means of interacting with their hosts and utilize a relatively static structure. While microbial carbohydrates offer a potential therapeutic target, their similarity to human carbohydrates require innovative methods for their selective application. The most common approaches to counter infectious disease rely on immunization, protection from infection, and post-infection therapy. Catabolically stable carbohydrates, important yet under exploited targets in controlling infectious disease, are the focus of this proposal. Sialic acid is a common ulosonic acid found at the non-reducing terminus of glycans in the glycocalyx, a carbohydrate shell surrounding animal cells, and in mucins, a highly charged glycoprotein barrier that protects certain tissues. Since glycoconjugates are both remodeled and catabolized from the non-reducing terminus by stepwise enzymatic removal of their saccharide units, the modification of their ulosonic acid component represents a target for blocking such transformation. The possible applications of stable ulosonic acid C-glycosides include: active and passive vaccines, the preparation of nanomaterials or coatings to target or provide a pathogen barrier, and as inhibitors of neuraminidases and hemagglutinins. This proposal describes the design, synthesis and preliminary evaluation of libraries of glycoconjugates containing ulosonic acid C-glycosides for use against pathogens. These molecules will also have impact on biomaterial applications. The specific aims are the preparation and evaluation of three target libraries: 1. alpha-2,8 C-linked sialic acid oligomers for use in the preparation of meningococcal vaccines; 2. mucin C-linked analogs as anti-infectives/barriers against type 2&3 pathogens and influenza; and 3.sialic acid C-glycosides as neuraminidase/hemagglutinin inhibitors & antiviral agents.